For a long time, a steam turbine driving method has been used in a mover of a cargo pump, but this method is based on two considered aspects. One aspect is the power demand of the mover and the other aspect is the ease of a rotation control in a full range from 0 to a maximum output and the necessity of an inert gas required by a rule.
In order to meet these demands, a full set of steam turbines including a cargo pump and an auxiliary boiler system covering a required amount of steam and an inert gas have been used in conventional systems.
The steam turbine of the mover of the cargo pump consumes a lot of steam. This steam is produced by an auxiliary boiler and the auxiliary boiler is supposed to cover the full demand of the steam turbine.
During the operation of the auxiliary boiler, the inert gas can be produced using an exhaust gas of this auxiliary boiler. According to a rule for following safety conditions of a cargo pipe for a cargo oil tank during cargo oil handling and other processes of cleaning the cargo oil sorting tank, the inert gas is supplied to a void space of the cargo oil sorting tank.
The fuel oil is consumed to produce the inert gas itself. If the inert gas is produced by other independent systems, the fuel oil consumption will be reduced due to this produced inert gas.
Patent Literature 1 discloses an auxiliary boiler system set on a shore to produce steam for a main cargo pump handling system. Also, a scrubber for producing an inert gas to be supplied into an oil tank is provided on a shore.
The invention disclosed in Patent Literature 1 decreases the weight of the oil tanker by employing a specific approach of removing the auxiliary boiler and the scrubber to save fuel consumed during normal sailing.